The field of the invention relates to a surgical device and method. More particularly, it relates to a tissue ablation probe and method for ablating a circumferential region of tissue at a location where a pulmonary vein extends from an atrium. The probe has particular utility during invasive or minimally invasive cardiac surgery.
Many local energy delivery devices and methods have been developed for the treatment of various abnormal tissue conditions in the body, and particularly for treating abnormal tissue along body space walls which define various body spaces in the body. For example, various devices have been disclosed with the primary purpose of treating or recanalizing atherosclerotic vessels with localized energy delivery. Several prior devices and methods combine energy delivery assemblies in combination with cardiovascular stent devices in order to locally deliver energy to tissue in order to maintain patency in diseased lumens such as blood vessels. Endometriosis, another abnormal wall tissue condition which is associated with the endometrial cavity and is characterized by dangerously proliferative uterine wall tissue along the surface of the endometrial cavity, has also been treated by local energy delivery devices and methods.
Several other devices and methods have also been disclosed which use catheter-based heat sources for the intended purpose of inducing thrombosis and controlling hemorrhaging within certain body lumens such as vessels. Detailed examples of local energy delivery devices and related procedures such as those of the types described above are disclosed in the following references: U.S. Pat. No. 4,672,962 to Hershenson; U.S. Pat. No. 4,676,258 to InoKuchi et al.; U.S. Pat. No. 4,790,311 to Ruiz; U.S. Pat. No. 4,807,620 to Strul et al.; U.S. Pat. No. 4,998,933 to Eggers et al.; U.S. Pat. No. 5,035,694 to Kasprzyk et al.; U.S. Pat. No. 5,190,540 to Lee; U.S. Pat. No. 5,226,430 to Spears et al.; and U.S. Pat. No. 5,292,321 to Lee; U.S. Pat. No. 5,449,380 to Chin; U.S. Pat. No. 5,505,730 to Edwards; U.S. Pat. No. 5,558,672 to Edwards et al.; and U.S. Pat. No. 5,562,720 to Stem et al.; U.S. Pat. No. 4,449,528 to Auth et al.; U.S. Pat. No. 4,522,205 to Taylor et al.; and U.S. Pat. No. 4,662,368 to Hussein et al.; U.S. Pat. No. 5,078,736 to Behl; and U.S. Pat. No. 5,178,618 to Kandarpa.
Other prior devices and methods electrically couple fluid to an ablation element during local energy delivery for treatment of abnormal tissues. Some such devices couple the fluid to the ablation element for the primary purpose of controlling the temperature of the element during the energy delivery. Other such devices couple the fluid more directly to the tissue-device interface either as another temperature control mechanism or in certain other known applications as a carrier or medium for the localized energy delivery. Detailed examples of ablation devices which use fluid to assist in electrically coupling electrodes to tissue are disclosed in the following references: U.S. Pat. No. 5,348,554 to Imran et al.; U.S. Pat. No. 5,423,811 to Imran et al.; U.S. Pat. No. 5,505,730 to Edwards; U.S. Pat. No. 5,545,161 to Imran et al.; U.S. Pat. No. 5,558,672 to Edwards et al.; U.S. Pat. No. 5,569,241 to Edwards; U.S. Pat. No. 5,575,788 to Baker et al.; U.S. Pat. No. 5,658,278 to Imran et al.; U.S. Pat. No. 5,688,267 to Panescu et al.; U.S. Pat. No. 5,697,927 to Imran et al.; U.S. Pat. No. 5,722,403 to McGee et al.; U.S. Pat. No. 5,769,846; and PCT Patent Application Publication No. WO 97/32525 to Pomeranz et al.; and PCT Patent Application Publication No. WO 98/02201 to Pomeranz et al.
Other prior devices and methods have been disclosed which use a probe as a surgical device, thereby allowing the physician to directly apply an electrode to tissue. Detailed examples of surgical probes are disclosed in the following references: U.S. Pat. No. 6,023,638 to Swanson; U.S. Pat. No. 4,841,979 to Dow et al.; U.S. Pat. No. 4,917,096 to Englehart et al.; and U.S. Pat. No. 6,152,920 to Thompson et al.
Atrial Fibrillation
Cardiac arrhythmias, and atrial fibrillation in particular, persist as common and dangerous medical ailments associated with abnormal cardiac chamber wall tissue. In patients with cardiac arrhythmia, abnormal regions of cardiac tissue do not follow the synchronous beating cycle associated with normally conductive tissue in patients with sinus rhythm. Instead, the abnormal regions of cardiac tissue aberrantly conduct electrical signals to adjacent tissue, thereby disrupting the cardiac cycle and causing an asynchronous cardiac rhythm. Such abnormal conduction is known to occur at various regions of the heart, such as, for example, in the region of the sino-atrial (SA) node, along the conduction pathways of the atrioventricular (AV) node and the Bundle of His, or in the cardiac muscle tissue forming the walls of the ventricular and atrial cardiac chambers.
Cardiac arrhythmias, including atrial arrhythmia, may be of a multiwavelet reentrant type, characterized by multiple asynchronous loops of electrical impulses that are scattered about the atrial chamber and are often self propagating. In the alternative or in addition to the multiwavelet reentrant type, cardiac arrhythmias may also have a focal origin, such as when an isolated region of tissue in an atrium fires autonomously in a rapid, repetitive fashion. Cardiac arrhythmias, including atrial fibrillation, may be generally detected using the global technique of an electrocardiogram (EKG). More sensitive procedures of mapping the specific conduction along the cardiac chambers have also been disclosed, such as, for example, in U.S. Pat. No. 4,641,649 to Walinsky et al. and in PCT Patent Application Publication No. WO 96/32897 to Desai.
A host of clinical conditions can result from the irregular cardiac function and resulting hemodynamic abnormalities associated with atrial fibrillation, including stroke, heart failure, and other thromboembolic events. In fact, atrial fibrillation is believed to be a significant cause of cerebral stroke, wherein the abnormal hemodynamics in the left atrium caused by the fibrillatory wall motion precipitate the formation of thrombus within the atrial chamber. A thromboembolism is ultimately dislodged into the left ventricle which thereafter pumps the embolism into the cerebral circulation where a stroke results. Accordingly, numerous procedures for treating atrial arrhythmias have been developed, including pharmacological, surgical, and catheter ablation procedures.
Several pharmacological approaches intended to remedy or otherwise treat atrial arrhythmias have been disclosed, such as, for example, those approaches disclosed in the following references: U.S. Pat. No. 4,673,563 to Beme et al.; U.S. Pat. No. 4,569,801 to Molloy et al.; and xe2x80x9cCurrent Management of Arrhythmiasxe2x80x9d (1991) by Hindricks, et al. Such pharmacological solutions, however, are not generally believed to be entirely effective in many cases, and are even believed in some cases to result in proarrhythmia and long term inefficacy.
Several surgical approaches have also been developed with the intention of treating atrial fibrillation. One particular example is known as the xe2x80x9cmaze procedure,xe2x80x9d as is disclosed by Cox, J. L. et al. in xe2x80x9cThe surgical treatment of atrial fibrillation. I. Summaryxe2x80x9d Thoracic and Cardiovascular Surgery 101(3), pp. 402-405 (1991); and also by Cox, J L in xe2x80x9cThe surgical treatment of atrial fibrillation. IV. Surgical Techniquexe2x80x9d, Thoracic and Cardiovascular Surgery 101(4), pp. 584-592 (1991). In general, the xe2x80x9cmazexe2x80x9d procedure is designed to relieve atrial arrhythmia by restoring effective atrial systole and sinus node control through a prescribed pattern of incisions about the tissue wall. In the early clinical experiences reported, the xe2x80x9cmazexe2x80x9d procedure included surgical incisions in both the right and the left atrial chambers. However, more recent reports predict that the surgical xe2x80x9cmazexe2x80x9d procedure may be substantially efficacious when performed only in the left atrium. See Sueda et al., xe2x80x9cSimple Left Atrial Procedure for Chronic Atrial Fibrillation Associated With Mitral Valve Diseasexe2x80x9d (1996).
The xe2x80x9cmaze procedurexe2x80x9d as performed in the left atrium generally includes forming vertical incisions from the two superior pulmonary veins and terminating in the region of the mitral valve annulus, traversing the region of the inferior pulmonary veins en route. An additional horizontal line also connects the superior ends of the two vertical incisions. Thus, the atrial wall region bordered by the pulmonary vein ostia is isolated from the other atrial tissue. In this process, the mechanical sectioning of atrial tissue eliminates the arrhythmogenic conduction from the boxed region of the pulmonary veins to the rest of the atrium by creating conduction blocks within the aberrant electrical conduction pathways. Other variations or modifications of this specific pattern just described have also been disclosed, all sharing the primary purpose of isolating known or suspected regions of arrhythmogenic origin or propagation along the atrial wall.
While the xe2x80x9cmazexe2x80x9d procedure and its variations as reported by Dr. Cox and others have met some success in treating patients with atrial arrhythmia, its highly invasive methodology is believed to be prohibitive in most cases. However, these procedures have provided a guiding principle that electrically isolating faulty cardiac tissue may successfully prevent atrial arrhythmia, and particularly atrial fibrillation caused by arrhythmogenic conduction arising from the region of the pulmonary veins.
Less invasive catheter-based approaches to treat atrial fibrillation have been disclosed which implement cardiac tissue ablation for terminating arrhythmogenic conduction in the atria. Examples of such catheter-based devices and treatment methods have generally targeted atrial segmentation with ablation catheter devices and methods adapted to form linear or curvilinear lesions in the wall tissue which defines the atrial chambers. Some specifically disclosed approaches provide specific ablation elements which are linear over a defined length intended to engage the tissue for creating the linear lesion. Other disclosed approaches provide shaped or steerable guiding sheaths, or sheaths within sheaths, for the intended purpose of directing tip ablation catheters toward the posterior left atrial wall such that sequential ablations along the predetermined path of tissue may create the desired lesion. In addition, various energy delivery modalities have been disclosed for forming atrial wall lesions, and include the use of microwave, laser, ultrasound, thermal conduction, and more commonly, radio frequency energies to create conduction blocks along the cardiac tissue wall.
Detailed examples of ablation device assemblies and methods for creating lesions along an atrial wall are disclosed in the following U.S. Patent references: U.S. Pat. No. 4,898,591 to Jang et al.; U.S. Pat. No. 5,104,393 to Isner et al.; U.S. Pat. No. 5,427,119; U.S. Pat. No. 5,487,385 to Avitall; U.S. Pat. No. 5,497,119 to Swartz et al.; U.S. Pat. No. 5,545,193 to Fleischman et al.; U.S. Pat. No. 5,549,661 to Kordis et al.; U.S. Pat. No. 5,575,810 to Swanson et al.; U.S. Pat. No. 5,564,440 to Swartz et al.; U.S. Pat. No. 5,592,609 to Swanson et al.; U.S. Pat. No. 5,575,766 to Swartz et al.; U.S. Pat. No. 5,582,609 to Swanson; U.S. Pat. No. 5,617,854 to Munsif; U.S. Pat. No. 5,687,723 to Avitall; U.S. Pat. No. 5,702,438 to Avitall. Other examples of such ablation devices and methods are disclosed in the following PCT Patent Application Publication Nos.: WO 93/20767 to Stem et al.; WO 94/21165 to Kordis et al.; WO 96/10961 to Fleischman et al.; WO 96/26675 to Klein et al.; and WO 97/37607 to Schaer. Additional examples of such ablation devices and methods are disclosed in the following published articles: xe2x80x9cPhysics and Engineering of Transcatheter Tissue Ablationxe2x80x9d, Avitall et al., Journal of American College of Cardiology, Volume 22, No. 3:921-932 (1993); and xe2x80x9cRight and Left Atrial Radiofrequency Catheter Therapy of Paroxysmal Atrial Fibrillation,xe2x80x9d Haissaguerre, et al., Journal of Cardiovascular Electrophysiology 7(12), pp. 1132-1144 (1996).
In addition to the known assemblies summarized above, additional tissue ablation device assemblies have been recently developed for the specific purpose of ensuring firm contact and consistent positioning of a linear ablation element along a length of tissue. This is accomplished by anchoring the element at least at one predetermined location along that length, such as in order to form a xe2x80x9cmazexe2x80x9d-type lesion pattern in the left atrium. An example of such an assembly is disclosed in U.S. Pat. No. 5,971,983 to Lesh, issued Oct. 26, 1999, which is hereby incorporated by reference. The assembly includes an anchor at each of two ends of a linear ablation element in order to secure those ends to each of two predetermined locations along a left atrial wall, such as at two adjacent pulmonary veins, so that tissue may be ablated along the length of tissue extending therebetween.
In addition to attempting atrial wall segmentation with long linear lesions for treating atrial arrhythmia, other ablation devices and methods have also been disclosed which are intended to use expandable members such as balloons to ablate cardiac tissue. Some such devices have been disclosed primarily for use in ablating tissue wall regions along the cardiac chambers. Other devices and methods have been disclosed for treating abnormal conduction of the left-sided accessory pathways, and in particular associated with xe2x80x9cWolff-Parkinson-Whitexe2x80x9d syndromexe2x80x94various such disclosures use a balloon for ablating from within a region of an associated coronary sinus adjacent to the desired cardiac tissue to ablate. Further more detailed examples of devices and methods such as of the types just described are variously disclosed in the following published references: Fram et al., in xe2x80x9cFeasibility of RF Powered Thermal Balloon Ablation of Atrioventricular Bypass Tracts via the Coronary Sinus: In vivo Canine Studies,xe2x80x9d PACE, Vol. 18, p 1518-1530 (1995); xe2x80x9cLong-term effects of percutaneous laser balloon ablation from the canine coronary sinusxe2x80x9d, Schuger CD et al., Circulation (1992) 86:947-954; and xe2x80x9cPercutaneous laser balloon coagulation of accessory pathwaysxe2x80x9d, McMath L P et al., Diagn Ther Cardiovasc Interven 1991; 1425:165-171.
Arrhythmias Originating from Foci in Pulmonary Veins
As briefly discussed above, various modes of atrial fibrillation have been observed to be focal in nature, caused by the rapid and repetitive firing of an isolated center within cardiac muscle tissue associated with the atrium. Such foci may act as either a trigger of atrial fibrillatory paroxysmal or may even sustain the fibrillation. Various disclosures have suggested that focal atrial arrhythmia often originates from at least one tissue region along one or more of the pulmonary veins of the left atrium, and even more particularly in the superior pulmonary veins.
Less invasive percutaneous catheter ablation techniques have been disclosed which use end-electrode catheter designs with the intention of ablating and thereby treating focal arrhythmias in the pulmonary veins. These ablation procedures are typically characterized by the incremental application of electrical energy to the tissue to form focal lesions designed to terminate the arrhythmogenic conduction.
One example of a focal ablation method intended to treat focal arrhythmia originating from a pulmonary vein is disclosed by Haissaguerre, et al. in xe2x80x9cRight and Left Atrial Radiofrequency Catheter Therapy of Paroxysmal Atrial Fibrillationxe2x80x9d in Journal of Cardiovascular Electrophysiology 7(12), pp. 1132-1144 (1996). Haissaguerre, et al. discloses radio frequency catheter ablation of drug-refractory paroxysmal atrial fibrillation using linear atrial lesions complemented by focal ablation targeted at arrhythmogenic foci in a screened patient population. The site of the arrhythmogenic foci were generally located just inside the superior pulmonary vein, and the focal ablations were generally performed using a standard 4 mm tip single ablation electrode.
Another focal ablation method of treating atrial arrhythmias is disclosed in Jais et al., xe2x80x9cA focal source of atrial fibrillation treated by discrete radio frequency ablation,xe2x80x9d Circulation 95:572-576 (1997). Jais et al. discloses treating patients with paroxysmal arrhythmias originating from a focal source by ablating that source. At the site of arrhythmogenic tissue, in both right and left atria, several pulses of a discrete source of radio frequency energy were applied in order to eliminate the fibrillatory process.
Other assemblies and methods have been disclosed addressing focal sources of arrhythmia in pulmonary veins by ablating circumferential regions of tissue either along the pulmonary vein, at the ostium of the vein along the atrial wall, or encircling the ostium and along the atrial wall. More detailed examples of device assemblies and methods for treating focal arrhythmia as just described are disclosed in PCT Patent Application Publication No. WO 99/02096 to Diederich et al., and also in the following Patents and pending U.S. Patent Applications: U.S. Ser. No. 08/889,798 for xe2x80x9cCircumferential Ablation Device Assemblyxe2x80x9d to Lesh et al., filed Jul. 8, 1997, now U.S. Pat. No. 6,024,740, issued on Feb. 15, 2000; U.S. Ser. No. 08/889,835 for xe2x80x9cDevice and Method for Forming a Circumferential Conduction Block in a Pulmonary Veinxe2x80x9d to Lesh, filed Jul. 8, 1997, now U.S. Pat. No. 6,012,457, issued Jan. 11, 2000; U.S. Ser. No. 09/199,736 for xe2x80x9cCircumferential Ablation Device Assemblyxe2x80x9d to Diederich et al., filed Feb. 3, 1998, now U.S. Pat. No. 6,117,101, issued Sep. 12, 2000; and U.S. Ser. No. 09/260,316 for xe2x80x9cTissue Ablation Device Assembly and Method of Forming a Conduction Block Along a Length of Tissuexe2x80x9d to Langberg et al., filed Mar. 1, 1999.
Another specific device assembly and method which is intended to treat focal atrial fibrillation by ablating a circumferential region of tissue between two seals in order to form a conduction block to isolate an arrhythmogenic focus within a pulmonary vein is disclosed in U.S. Pat. No. 5,938,660 and a related PCT Patent Application Publication No. WO 99/00064. The disclosures of these references are herein incorporated in their entirety by reference thereto.
The device assemblies and methods disclosed heretofore for ablating a circumferential region of tissue generally involve catheter-based therapies wherein an ablation element is mounted on the distal end of the catheter for placement in a pulmonary vein, such as in a percutaneous translumenal procedure. However, in certain surgical approaches, such as trans-thoracic surgery, a physician can access the pulmonary vein in a more direct manner, such as through an atriotomy, thereby obviating the need for a catheter-based device. None of the disclosed circumferential ablation devices provides a device assembly or method that can be used to directly place an ablation element in a pulmonary vein during trans-thoracic or minimally invasive cardiac surgical procedures.
Thus, a need exists for a rigid, handheld surgical probe for delivering ablative energy at a location where a pulmonary vein extends from an atrial wall. It is desirable that such a surgical probe be adapted to precisely deliver ablative energy to form a circumferential lesion to treat atrial fibrillation.
The preferred embodiments of the present invention provide a ergonomically designed, handheld surgical ablation probe that is substantially rigid and can be used to directly apply ablative energy to form a circumferential lesion in a pulmonary vein during trans-thoracic or minimally invasive surgery. The preferred embodiments are provided with a deflectable tip for enhanced maneuverability and precise placement of the ablation element in a pulmonary vein. The preferred embodiments also include an expandable member on the distal end for anchoring the ablation element to the surrounding tissue during ablation. The surgical ablation probe is adapted for use with various types of ablation elements, such as, for example, an ultrasonic transducer.
One aspect of the present invention involves a medical device system for ablating a circumferential region of tissue in order to form a circumferential conduction block at a location where a pulmonary vein extends from an atrium in a patient""s heart. Such conduction block may be formed in order to, for example: electrically isolate a focal source of arrhythmia in the pulmonary vein from the rest of the atrium; or connect linear lesions such that a pattern of conduction blocks may be formed to isolate a posterior region of the atrial wall from the rest of the atrium.
In one mode, a tissue ablation probe of the present medical device system ablates a substantial portion of a circumferential region of tissue at a location in a patient""s body where a pulmonary vein extends from an atrium in a patient. The ablation probe includes a handle attached to a proximal end portion of a relatively short shaft (i.e., short as compared to a percutaneous translumenal catheter). An ablation member is coupled to a distal end portion of the shaft. The ablation member also comprises an expandable member coupled to the distal end portion of the shaft, wherein the expandable member is adjustable from a collapsed position to an expanded position. The expandable member is adapted to engage a substantial portion of the circumferential region of tissue when in the expanded position. The ablation member also has an ablation element that is adapted to ablate at least a portion of the substantial portion of the circumferential region of tissue.
The ablation element employed in differing modes of the tissue ablation probe can comprise a microwave ablation element, a cryogenic ablation element, a thermal ablation element, a light-emitting ablation element (e.g., laser), an ultrasound transducer, or an electrical ablation element, such as an RF ablation element.
In one mode of the ablation apparatus, the expandable member is an inflatable balloon. The expandable member can have an outer surface that is adapted to contact the substantial portion of the circumferential region of tissue along an ablative path when the expandable member is adjusted to the expanded position.
The ablation member may also include a sensor that is coupled to the expandable member at a location at least when the expandable member is in the expanded position. A conductor is coupled to the sensor in a manner that does not substantially affect the adjustment of the expandable member from the collapsed positioned to an expanded position. In a preferred form, the conductor also is coupled to a coupler at the proximal end portion of the handle.
In a preferred mode, the ablation element preferably comprises an ultrasound transducer adapted to emit a circumferential path of ultrasound ablative energy. The sensor may be positionable within the circumferential path when the expandable member is in the expanded position.
In accordance with one method of using the ablation probe of the present invention, during a trans-thoracic (open heart) or minimally invasive cardiac procedure, e.g., for mitral valve replacement, a physician can place the distal end of the shaft, including the ablation member, at a location where a pulmonary vein extends from an atrium. The expandable member is expanded to secure and/or ablatively couple the ablation member to the location and the ablation element is energized to ablate at least a substantial portion of the circumferential region of tissue.
Also disclosed is a method for monitoring the ablation of a substantial portion of a circumferential region of tissue at a location where a pulmonary vein extends from an atrium. The method involves positioning an ablation member, which has an ablation element, along the location where the pulmonary vein extends from the atrium. The ablation element is activated to ablate the substantial portion of the circumferential region of tissue. This can be done simultaneously or through a sequential series of ablation steps (temporal and/or spatial). Temperature is monitored along the substantial portion of the circumferential region of tissue. The ablation element is deactivated when the temperature along the substantial portion of the circumferential region of tissue has reached either a first predetermined value or a second predetermined valve for a predetermined period of time.
While various aspects and features of the present invention have particular utility in the context of tissue ablation apparatuses and ablation processes, such aspects and features also can be practiced apart from such devices and methods.
Various aspects, features and advantages of the present invention, in addition to those described above, will also become apparent from the following description of preferred modes of the invention and from the appended description.